Visualização de escoamento turbulento de fluido newtoniano em contrações abruptas com a técnica PIV

Abstract

Abrupt contractions are largely used in pipes and equipment in industrial processes involving the flow of Newtonian and non-Newtonian fluids. This work aims to study the water flow in abrupt contractions with contraction ratios β=2,27 e 4,39. To visualize the flow the PIV technique was used that consists in acquire pairs of images at a certain time interval of particles added to the flow which are illuminated by a laser plane. Correlations which identify the particles in the two images are used, measuring its displacement and, from it, the velocity vector is calculated. To validate the technique were performed tests on water with smooth pipe for turbulent flow at Reynolds numbers Re=4900, 10000, 17800 and 24600. In abrupt contraction with contraction ratio β=2,27, tests were conducted at Reynolds numbers amount of contraction ReD=4900, 10000, 17800 and 24600. In abrupt contraction with contraction ratio β=4,39, tests were conducted at Reynolds numbers amount of contraction ReD=4900, 7500, 10000 and 13500. From the velocity vector maps obtained by the PIV system, results are presented as velocity scalar maps and average velocity profiles in the region of the tube upstream the contraction, which could be observed the flow development as approaches the contraction. The differential pressure was also measured in order to calculate the pressure drop coefficient of contraction. The results were satisfactory compared to the literature. The PIV technique has proven effective on velocity fields visualization